Filter device for clarifying contaminated liquids

ABSTRACT

A filter device for the clarification of contaminated liquids includes a plurality of disk-shaped filter elements spaced apart from one another and combined into circular or polygonal filter modules. The filter elements are arranged rotatably about a horizontal axis in a vessel containing the unclarified liquid. The filtrate is capable of being discharged via the individual filter modules. The filter modules form centrally a cavity. The cavity on one side is closed by a carrying disk and on the other side is connected to the vessel via a suction-intake orifice. The cavity is connected operatively to a flow member in such a way that, via the suction-intake orifice, a flow can be generated in the unclarified liquid between the spaced-apart filter elements and avoids an adhesion of solids to the filter elements.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to filter devices which are used for the clarification of contaminated liquids, in particular in sewage purification and water treatment.

Filter devices of this type consist of a plurality of filter elements which are spaced apart from one another and which are combined into filter modules and are arranged rotatably in a circular or polygonal form of construction in a vessel containing the filter liquid. The filter elements consist of filter disks which are equipped on both sides with filters and which have grooves for discharging the filtrate. At the commencement of the rotational movement of the filter modules in the still stationary filter liquid, a flow resistance occurs on the filter surfaces which initially prevents solids retained on the filter surfaces from being deposited due to the high relative speed between the filter device and the liquid. With an increasing period of rotation of the filter device, however, the initial flow resistance decreases, because the filter liquid is circulated to an increasing extent and the relative speed between the filter device and the liquid becomes lower, so that, as the filter time progresses, what may be referred to as covering layers of solids are formed on the filters and are detrimental to the efficiency of the filter device.

It is known from DE 195 37 578, for the elimination of the filtration-inhibiting covering layer on the filters, to provide on the filters a backwash device consisting of a plurality of suction-extraction bars which bear on the filters on both sides of the filter disk and extend radially from the outside inward. The individual suction-extraction bars are connected to downpipes and are connected to a suction pump via further pipeline systems. By built-in slides in the downpipes being opened, clarified liquid is forced out of the interior of the filter disks into the suction-extraction bars, in order thereby to free the filter surfaces of the adhering solid layers. If cleaning is insufficient, backwashing may be further reinforced by the connected suction pump. In this cleaning process, the suction-extraction bars cause mechanical wear at the filters and thus impair their useful life. In addition to the backwash device, a device for the intensive cleaning of the filters is also provided. This consists of a set of injection pipes which are extended vertically as far as the hollow shaft and the spray nozzles of which are fed with already clarified liquid by a high-pressure pump. One disadvantage of this is that the clarified liquid used for cleaning the filters, due to being enriched with solids, flows back into the vessel again and undergoes a filter process once more, thus leading to a reduction in filter capacity. The outlay involved in the backwash and intensive-cleaning device in mechanical and control terms is appreciable. The result of discontinuous cleaning is that during the filter process, between the cleaning phases, new covering layers of retained solids are repeatedly formed on the filters and have an adverse influence on the efficiency of the filter process.

Furthermore, EP-A-0 289 674 discloses a filter device which operates according to the centrifuge principle. For this purpose, a hollow shaft, on which filter elements are fastened, spaced apart, next to one another, is rotatably arranged vertically in a closed vessel. The hollow shaft has, below the vessel, an inlet valve for supplying the filter liquid and, above the vessel, an inlet valve for supplying a backwashing agent. First, with the inlet valve for the backwash closed, filter liquid is introduced into the hollow shaft via the lower inlet valve. As a result of the centrifugal force occurring during rotation, the filter liquid passes through the holes of the hollow shaft and infiltrates between the adjacent filter elements. The centrifugal force causes external pressure to be exerted on the filter disks, so that the filtrate penetrates into the interior of the filter disks, is discharged on the periphery of the disks by means of pipelines and is intercepted in a trough above the closed vessel, from where it can flow away. During the filter operation, even here, filtration-inhibiting covering layers are formed on the filter surfaces and, as the filter time progresses, inhibit the filter process. Backwashing is therefore regularly necessary. The supply of filter liquid is interrupted for the time of the backwash and a backwashing medium is introduced under high pressure into the hollow shaft via the inlet valve for the backwash, which backwashing medium consists of either clear filtrate, air or gas and flows out via the holes in the hollow shaft between the adjacent filter disks and thus eliminates the filtration-inhibiting covering layers from the filter surfaces. The backwash entails a relatively high technical outlay. Moreover, the efficiency of the filter process is impaired.

SUMMARY OF THE INVENTION

The object on which the invention is based is, while avoiding the disadvantages of the prior art, to provide a filter device for the clarification of contaminated liquids, by means of which automatic, continuous and wear-free cleaning of the filters is achieved and which thus prevents the situation where, during the filter operation, filtration-inhibiting solid deposits (covering layers), which have an adverse influence on the filter process, are formed on the filters.

The object is achieved, according to the invention, in that the filter modules form centrally a cavity which on one side is closed by means of a carrying disk and on the other side is connected to the vessel via a suction-intake orifice, and in that the cavity is connected operatively to a flow member in such a way that, via the suction-intake orifice, a flow can be generated in the unclarified liquid between the spaced-apart filter elements and avoids an adhesion of solids to the filter elements.

As a result, constant flow resistance is generated due to the swirling of the unclarified liquid between the adjacent filter elements, and automatic, continuous and wear-free cleaning of the filters is brought about without any mechanical action. Filtration-inhibiting covering layers due to solid deposits on the filters thus remain avoided, so that the filtration efficiency is improved. Only the unclarified liquid in the vessel serves for the cleaning process, so that already clarified liquid no longer has to be returned into the filter circuit, with the result that the filter capacity is increased, as compared with conventional filter devices. The invention can be implemented without a high technical outlay and at low costs and, moreover, is maintenance-friendly. Expediently, the filter modules are lined up on rods and are supported, on the one hand, in a bearing via a driveshaft connected firmly to the carrying disk and, on the other hand, in a bearing via a bearing flange having the suction-intake orifice.

Advantageously, the flow member is designed as a pump vane wheel and is connected to a driveshaft via the carrying disk connected to the filter modules. A pump action is thereby generated at the same time by means of the filter device and during the filter operation causes an intensive flow of the filter liquid through between the spaced-apart filter elements, with a cleaning effect taking place simultaneously. By virtue of the integrated pump vane wheel, a separate drive becomes unnecessary and the costs are reduced.

According to a further feature of the invention, an axial vane wheel connected to a separate motor is arranged in the suction-intake orifice of the bearing flange. Consequently, the rotational speed of the flow member can be regulated, irrespective of the rotational speed of the filter device, and the flow velocity of the filter liquid on the filter surfaces can thus be controlled.

According to another feature, there is provision for a flow duct to be inserted through the suction-intake orifice of the bearing flange and to be fastened in a support bearing, the flow duct being connected, on the one hand, to the vessel by means of a suction-intake orifice and, on the other hand, to the cavity by means of a slot-shaped orifice. As a result, an even higher flow velocity can be achieved between the filter elements and the cleaning effect can be further intensified.

Finally, according to a last feature, there is provision for a flow duct to be inserted through the suction-intake orifice of the bearing flange and to be fastened in a support bearing, the flow duct being connected by means of a suction-intake orifice to a pipeline which issues with a suction-intake orifice below the filter device on the vessel, and a liquid pump being integrated into the pipeline.

The invention will be explained in more detail below by means of an exemplary embodiment with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagrammatic illustration of the filter device with a pump vane wheel;

FIG. 2 shows a design variant with a separately driven axial vane wheel;

FIG. 3 shows a design variant with a built-in flow duct and possible arrangements of the flow members;

FIG. 4 shows a design variant with a flow duct and an integrated pump; and

FIG. 5 shows a section along the line I—I according to FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The filter device 1 is accommodated rotatably in a vessel 2 containing the filter liquid. In this case, a plurality of filter modules 3 are arranged circularly. The filter modules 3 are composed of individual filter elements 4 with a spacing of preferably 4 to 8 mm. The filter elements 4 consist of known filter disks, not illustrated in the drawing, via which the filtrate is discharged and which are equipped on both sides with filters. The spacing between the filter elements 4 is produced by means of spacer disks 5. The filter modules 3 are delimited, on the one hand, by a carrying disk 6 and, on the other hand, by a bearing flange 7 and are fastened by means of rods 8 and nuts 9. The carrying disk 6 is firmly connected to a driveshaft 10 and is supported rotatably in a bearing 11.

The bearing flange 7 has a suction-intake orifice 12 and is guided in a bearing 13. A cavity 14 formed by the filter modules 3 is connected via the suction-intake orifice 12 to the vessel 2 containing the filter liquid. Arranged in the cavity 14 is a flow member which is designed as a pump vane wheel 15 and which is connected to the driveshaft 10 via the carrying disk 6. The individual filter elements 4 are connected to suction-extraction lines 16 which are connected to duct strips 17 fastened to the carrying disk 6 and which issue onto the end-face pipelines 18 which run on the end face of the carrying disk 6 in a star-shaped manner according to the number of filter modules 3 and which are fastened on the driveshaft 10. The pipelines 18 are connected via connecting ducts 19 and a sliding ring 20 which is arranged on the driveshaft 10 and to which is connected a further pipeline 21 leading to a vacuum pump 22. The filter device 1 is connected to a chain drive 23 via the driveshaft 10 (FIG. 1).

In a further design possibility according to FIG. 2, there is provision for an axial vane wheel 24, which is driven separately via a motor 25, to be arranged in the suction-intake orifice 12 of the bearing flange 7.

In an embodiment according to FIG. 3, a flow duct 26 is pushed in the suction-intake orifice 12 and has a suction-intake orifice 27 which is fastened to a support bearing 28. The cavity 14 is in this case connected to the suction-intake orifice 27 via a slot-shaped orifice 29. Both a pump vane wheel 15 and a motor-driven axial vane wheel 24 can be operated via the flow duct 26. FIG. 4 shows a further embodiment, in which the flow duct 26 is connected to a pump 31 via a pipeline 30 and issues through a suction-intake orifice 32 in the lower region of the vessel 2.

Operation is as follows:

During the rotational movement of the filter device 1, filtrate from the vessel 2 is sucked in via the vacuum pump 22, penetrates via the filters of the filter elements 4 and is discharged via suction-extraction lines 16, duct strips 17, pipelines 18, connecting ducts 19, the sliding ring 20 and the pipeline 21. The filter liquid in the vessel 2 is kept constant via an inflow 33. By means of the flow members provided, a defined flow between the spaced-apart filter elements is generated in the filter liquid via the suction-intake orifices 12, 27, 32, so that the solids attracted by the filter suction effect do not remain adhering to the filters and are constantly entrained by the liquid flow. As a result, during the entire filter operation, an automatic and continuous cleaning effect is achieved, without any action of wear on the filters. In addition to a relatively low investment outlay, as compared with conventional generic filter devices, the energy outlay is in this case also markedly reduced and the efficiency of the filter device is increased. By the avoidance of backwashing and intensive cleaning by means of clarified water, the filter capacity is increased. 

1. A filter device for the clarification of contaminated liquids, comprising: a plurality of disk-shaped filter elements spaced apart from one another and combined into circular or polygonal filter modules and arranged rotatably about a horizontal axis in a vessel containing the unclarified liquid, the filtrate being capable of being discharged via the individual filter modules; the filter modules forming centrally a cavity, the cavity on one side being closed by a carrying disk and on the other side being connected to the vessel via a suction-intake orifice, and the cavity being connected operatively to a flow member in such a way that, via the suction-intake orifice, a flow can be generated in the unclarified liquid between the spaced-apart filter elements and avoids an adhesion of solids to the filter elements; and wherein said carrying disk is in the form of a flat plate that extends completely across said one side of the cavity.
 2. A filter device for the clarification of contaminated liquids, comprising: a plurality of disk-shaped filter elements spaced apart from one another and combined into circular or polygonal filter modules and arranged rotatable about a horizontal axis in a vessel containing the unclarified liquid, the filtrate being capable of being discharged via the individual filter modules; the filter modules forming centrally a cavity, the cavity on one side being closed by a carrying disk and on the other side being connected to the vessel via a suction-intake orifice, and the cavity being connected operatively to a flow member in such a way that, via the suction-intake orifice, a flow can be generated in the unclarified liquid between the spaced-apart filter elements and avoids an adhesion of solids to the filter elements; and wherein the filter modules are lined up on rods and are supported, on the one hand, in a bearing via a driveshaft connected firmly to the carrying disk and, on the other hand, in a bearing via a bearing flange having the suction-intake orifice.
 3. The filter device as claimed in claim 2, wherein the flow member is a pump vane wheel and is connected to the driveshaft via the carrying disk connected to the filter modules.
 4. The filter device as claimed in claim 2, wherein an axial vane wheel connected to a separate motor is arranged in the suction-intake orifice of the bearing flange.
 5. The filter device as claimed in claim 2, wherein a flow duct is inserted trough the suction-intake orifice of the bearing flange and is fastened in a support bearing, the flow duct being connected, on the one hand, to the vessel by a suction-intake orifice and, on the other hand, to the cavity by a slot-shaped orifice.
 6. The filter device as claimed in claim 2, wherein a flow duct is inserted through the suction-intake orifice of the bearing flange and is fastened in a support bearing, the flow duct being connected by a suction-intake orifice to a pipeline which issues with a suction-intake orifice below the filter device on the vessel, and a liquid pump being integrated into the pipeline. 